Such apparatus generally comprise a casing inside which is a combustion chamber, also known as a heating body, designed to accommodate in its lower part at least one burner in which the gas is ignited and control devices for the gas supply. The products of combustion pass through the heating body and heat exchange takes place with the surrounding air in contact with the walls of the heating body. The said products of combustion then pass through a box known as a flame damper generally situated at the back of the heating body and connected to the latter by one or more channels or collecting pipes. Such a box generally comprises a device for reducing the effect of the draught and if necessary preventing any deleterious influence of the backflow wind on the operation of the burner and on combustion. The box also contains a discharge pipe for productions of combustion designed to be connected to a suitable smoke pipe.
It will readily be seen that the manufacture of such a box with outflow parts and parts requiring to be connected to the back of the heating body is expensive.
Moreover, since this box adds to the depth of the heating body and is generally covered by the casing, the cost of the casing will increase according to the depth of the box. In addition. the box adds to the bulk and weight of the whole apparatus, which is reflected in the cost of packaging, storage and transport.
A box containing the damping devices and integrated in a heating body has been disclosed in U.S. Pat. No. 3 536 060. The said Patent, however, describes a boiler in which the effective heat exchange is obtained entirely from the heat exchange tubes in which a fluid exchange medium circulates. The walls of this box which carries the discharge pipe do not contribute to the useful thermal yield of the boiler, and the calorific wastage of the walls constitute a loss of effective yield.